1. Field of the Invention
The present invention relates to a sampling frequency converter which converts input data sampled by sampling pulses having a sampling frequency of 32 kHz or 48 kHz into output data sampled by sampling pulses having a sampling frequency of 44.1 kHz.
2. Related Background Art
FIG. 3 shows a conventional sampling frequency converter which converts input data sampled by sampling pulses having a sampling frequency of 32 kHz or 48 kHz into output data sampled by sampling pulses having a sampling frequency of 44.1 kHz. As shown in FIG. 3, input data sampled by sampling pulses having a sampling frequency of 32 kHz is over-sampled by a three-fold by an over-sampling filter 21, and the output of the over-sampling filter 21 is down-sampled by a one-2nd-fold by a down-sampling filter 22. The output of the down-sampling filter 22 and input data sampled by sampling pulses having a sampling frequency of 48 kHz are supplied to a selector 23. The data selected by the selector 23 is over-sampled by a 147-fold by an over-sampling filter 24 and down-sampled by a one-160th-fold by a down-sampling filter 25. In this manner, the output data sampled by sampling pulses having a sampling frequency of 44.1 kHz is obtained.
In obtaining an analog signal converted from data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 48 kHz by using the conventional sampling frequency converter 40, and in recording data sampled by sampling pulses having a sampling frequency of 44.1 kHz in a recording medium, the circuit shown in FIG. 4 has been used. Namely, input data sampled by sampling pulses having a frequency of 48 kHz is over-sampled by an over-sampling filter 26 to obtain output data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 48 kHz, and the over-sampled data is converted into an analog signal by a D/A converter 27.
In obtaining an analog signal converted from data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 44.1 kHz, and in recording data sampled by sampling pulses having a sampling frequency of 44.1 kHz in a recording medium, the circuit shown in FIG. 5 has been used. Namely, the output data converted by the sampling frequency converter 40 into the data sampled by sampling pulses having a sampling frequency of 44.1 kHz is over-sampled by an over-sampling filter 28 to obtain data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 44.1 kHz, and the over-sampled data is converted into an analog signal by a D/A converter 29.
In recording data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 44.1 kHz in a recording medium, the circuit shown in FIG. 6 has been used. Namely, the output data converted by the sampling frequency converter 40 into the data sampled by sampling pulses having a sampling frequency of 44.1 kHz is over-sampled by an over-sampling filter 30 to obtain data sampled by sampling pulses having a sampling frequency of 2-, 4-, or 8-fold of 44.1 kHz, and the over-sampled data is encoded by an encoder 31.
The conventional circuits shown in FIGS. 4 to 6 require the over-sampling filter which is associated with the problem of degrading the characteristics of sampled data.